The present invention relates to a new and improved construction of an immersible probe for optical dual beam-measuring apparatus, which is of the type comprising a sample feeler intended to be immersed in a sample to be analyzed and for carrying out a measurement thereat, the sample feeler being equipped with a light conductor.
Equipment of this general type is used in photometry, turbidimetry and for the performance of photo titrations. As a general rule the analysis is carried out while working with liquid samples.
In order to obtain satisfactorily accurate and reproducible measurement results when working with dual beam-measuring apparatuses the measurement signal is compared with a reference signal and the relationship of both signals to one another is evaluated. With a state-of-the-art arrangement the reference signal is directly derived from the common light source. With this technique it is only possible to eliminate instabilities of the light source as a possible source of error adversely effecting the measurement result. However, such type of arrangement can only be designated with qualification as a dual beam-measuring apparatus. True dual beam-measuring apparatuses of the prior art are classified as that type of equipment where the light penetrates through both a sample cuvette and a reference cuvette. Apart from errors attributable to the light source it is then also possible to compensate such predicated, for instance, upon the nature and properties of the solvent which is employed.
With analysis equipment utilizing immersible probes additional errors exist which typically result from the light path both leading to and from the sample sensor, which light paths normally are quite long.
Furthermore, it is in principle advantageous and desirable to carry out to the extent possible a separation of the "wet" part (sample and standard or reference medium) and "dry" part (control component), and furthermore, to design the equipment such that handling of the standard or reference medium is simple.